Ao Smith 100074218 Burner Window Tankless Water Heater

Product Description

The AO SMITH 100074218 is a replacement burner window designed for use in AO Smith tankless water heater units. The burner window provides a sealed viewing port in the combustion chamber assembly, allowing technicians to inspect burner operation without compromising the integrity of the heat exchanger enclosure. This part is a direct OEM-style replacement intended for field service and routine maintenance. Licensed plumbers and HVAC technicians performing burner assembly service or combustion inspection work will encounter this component on both natural gas and LP-fired AO Smith tankless models across multiple product lines.

This burner window is compatible with a wide range of AO Smith tankless water heater models spanning indoor, outdoor, direct-vent, and open-combustion configurations in both natural gas and liquid propane fuel types. The part covers residential and light commercial tankless units from the T-series and TK-series product families. Verified compatible models are listed in the compatibility section below.

Key Features

• Direct OEM replacement part for AO Smith tankless water heater burner assemblies
• Compatible with both natural gas and LP-fired units across multiple model variants
• Supports indoor, outdoor, direct-vent, and open-combustion installation configurations
• Designed for field service and maintenance applications

Compatibility

Verified compatible with the following AO Smith tankless water heater models: T-H3M-DV (LP), T-K3-SP (LP), TK-540P-NEH (NG), TK-310U-I (NG/LP), TK-110U-I (NG/LP), T-M50 (NG), T-D2U-OS (NG), T-H3J-OS (LP), T-KJR2-IN (NG), T-KJR2U-OS (NG), TK-540P-PIH (LP), TK-510U-E (NG/LP), T-H3S-DV (LP), T-M32-ASME (LP), T-H2S-OS (LP), T-K4-IN (LP), T-H2-DV (LP), T-K3-OS (NG), T-K3-OS (LP), T-H3M-OS (LP), TK-540P-NIH (NG), TK-310U-E (NG/LP), T-H2-OS (NG), T-M32-ASME (NG), T-H2S-DV (NG), T-K4-OS (NG), T-H3-OS (NG), TK-510U-I (NG/LP), TK-110U-E (NG/LP), T-K4U-OS (NG), T-H2-OS (LP), T-M50-ASME (LP), T-M32 (LP), T-H3-DV (NG), T-H3M-OS (NG), T-K4U-IN (NG), T-H3-DV (LP), T-H2S-DV (LP), T-H3M-DV (NG), T-H2S-OS (NG), T-D2-OS (LP), T-H3J-OS (NG), T-K3-SP (NG), T-H2-DV (NG), T-M50 (LP), T-K3-PRO (LP), T-H3S-OS (NG), T-D2-IN (LP), T-H3J-DV (LP), T-M32 (NG), T-H3S-OS (LP), T-K4-IN (NG), T-M50-ASME (NG), T-K4-OS (LP), T-KJR2U-IN (NG), T-K3 (LP), T-D2-IN (NG), T-KJR2-OS (LP), T-H3J-DV (NG), T-D2-OS (NG), T-H3S-DV (NG), T-KJR2-IN (LP), T-K3-PRO (NG), T-H3-OS (LP), T-KJR2-OS (NG), T-D2U-IN (NG), T-K3 (NG), TK-540P-PEH (LP).

Installation Notes

Burner window replacement on tankless water heaters should be performed by a licensed plumber or qualified HVAC technician. Before beginning any burner assembly service, shut off the gas supply at the service valve and disconnect power to the unit. Allow the heat exchanger and combustion chamber to cool fully before handling internal components. Verify the replacement part seats and seals correctly before restoring gas and power and performing a test fire.

Technical Specifications

• Application: Replacement Part

Standard Information

• Brand: AO SMITH
• Manufacturer Part Number: 100074218